Even in a country with no shortage of no-go areas, human rights investigators, diplomats and journalists agree the hardest place of all from which to get accurate information is Pakistan’s Balochistan province.

State security agencies heavily restrict outsiders’ access to the resource rich region and lean on local media to ignore claims made by separatist insurgents unless confirmed by the authorities.

Supporters of independence for Balochistan claim the province has been deliberately turned into an information “black hole” to prevent discussion of Baloch grievances at home and abroad.

Bibi Gul, an activist at the Baloch Human Rights Organisation, tries to get around the restrictions through an informal network of smartphone users who distribute short audio news bulletins via apps such as Blackberry Messenger.

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If the dozens of messages generated by the system in mid-December had a lead story, it was an angry rejection of government claims that 13 people killed in the district of Arawan had been insurgent fighters. “It is a blatant lie,” a male voice growled from Gul’s phone. “They were unarmed civilians. The army raided houses and humiliated the women.”

On a busy day Gul receives up to 30 short audio messages describing alleged human rights abuses by security forces, which she promptly forwards to 15 other people, who in turn send it on to yet more people.

They also include highly sensitive reports about the movements of security forces as they approach villages. “We issue early warnings to local people so they can protect themselves,” she said.

Few of the claims of killings and kidnappings of civilians by security forces that pass through Gul’s phone are covered by Pakistan’s domestic media.

Journalists in Quetta, the provincial capital, say they cannot confirm most claims made by separatists because they have limited access to insurgent hotspots. They also say their lives are at risk if they do not report the version of events provided by state agencies.

Pakistani paramilitary soldiers last month salute the coffins of colleagues killed in a roadside blast in Quetta, the capital of Balochistan province. Photograph: Banaras Khan/AFP/Getty Images

According to Amnesty International, 12 journalists have been killed in Balochistan for doing their jobs since 2008. Mustafa Qadri from Amnesty said the province is the hardest place in the country for human rights researchers to operate. “State and non-state actors exploit the lawlessness and remoteness of these areas to stifle independent investigation of what is happening on the ground,” he said.

In recent years it has become increasingly rare for foreign diplomats and journalists to be given the “no objection certificates” required to visit Balochistan.

During a visit to Gwadar, a strategic port near the Iranian border, the Guardian was prevented from reporting outside the confines of a hotel, despite the trip being covered by a no objection certificate issued by the information ministry in Islamabad.

Officials say the system is necessary to ensure the security of visitors. But it also limits scrutiny of a province that hosts senior members of the Afghan Taliban and is rife with sectarian and nationalist militancy. Personnel from up to four different civilian and military intelligence agencies aggressively monitor foreign visitors, demanding details of stories and interviews.

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A local journalist working with the Guardian was even shown his recent call history by an intelligence agent and was warned of repercussions if any stories “damaged the integrity of the country”.

Many interviewees are unwilling to meet under such heavy surveillance. ­

“The [security] establishment is very touchy about anyone challenging their narrative that everything they are doing is good for Balochistan,” said Mohammad Ali Talpur, an activist and veteran of the insurgency that broke out in the 1970s.

Talpur was recently dropped as a columnist by the Daily Times, which he says was due to official pressure on the newspaper. “Anger in the province has never been greater but they don’t want anyone to know about it,” he said.

Two Indian journalists had their visas revoked in May 2014 because they had been “promoting stories about Balochistan in India”, according to one senior member of the government in Islamabad.

In April one of Pakistan’s leading universities cancelled a seminar featuring Abdul Qadeer Baloch, the head of Voice for Baloch Missing Persons – which campaigns against the abduction of suspected militants and their supporters – after coming under pressure from the state’s most powerful intelligence agency.